working dos vga writes!

Common/Snd/oscs.h

@@ -0,0 +1,91 @@
+/*
+  Dinky fixed point oscillators.
+  https://git.poto.cafe/veclavtalica/stfu/src/branch/master/Source/oscillators.c
+*/
+
+#ifndef COM_SND_OSCS_H
+#define COM_SND_OSCS_H
+
+#include "../cfg.h"
+#include "../fix.h"
+#include "../std.h"
+#include <stdint.h>
+
+/* Intended to be executed offline with values then embedded in the binary. */
+struct com_snd_swave {
+  uint16_t f, s, c;
+};
+
+static struct com_snd_swave
+com_snd_swave_init(com_fix_t frequency, uint16_t phase, uint16_t amplitude) {
+  com_std_assert(frequency > 0);
+  struct com_snd_swave r;
+  r.f = 2.f * sinf((float)M_PI * frequency / STFU_AUDIO_FRAME_RATE);
+  r.s = amplitude * sinf(phase);
+  r.c = amplitude * cosf(phase);
+  return r;
+}
+
+static inline int16_t com_snd_swave_pump(struct com_snd_swave *wave) {
+  int16_t const f = com_fix_sin(com_fix_mul(
+      wave->phase, com_fix_div(com_fix_mul(wave->frequency, COM_FIX_PI2),
+                               COM_CFG_SNDFRMRATE)));
+  wave->phase += 1;
+  return f;
+}
+
+/* Implemented over sinewave */
+// struct com_snd_oscs_sqrtwave {
+//   struct com_snd_swave w;
+//   union {
+//     float f;
+//     uint32_t u;
+//   } v;
+// } com_snd_oscs_init_sqrtwave(float frequency, float phase, float amplitude) {
+//   struct com_snd_oscs_sqrtwave r;
+//   union {
+//     float f;
+//     uint32_t u;
+//   } v, a;
+//   r.w = com_snd_oscs_init_sinewave(frequency, phase, 1.f);
+//   v.f = r.w.s;
+//   a.f = amplitude;
+//   r.v.u = (a.u & 0x7fffffff) | (v.u & 0x80000000);
+//   return r;
+// }
+
+// /* Use floating point bit representation to infer sign, all other bits are
+// set
+//  * to amplitude */
+// struct com_snd_oscs_sqrtwave
+// com_snd_oscs_pump_sqrtwave(struct com_snd_oscs_sqrtwave wave) {
+//   union {
+//     float f;
+//     uint32_t u;
+//   } v;
+//   com_snd_oscs_pump_sinewave(wave.w);
+//   v.f = wave.w.s;
+//   wave.v.u = (wave.v.u & 0x7fffffff) | (v.u & 0x80000000);
+//   return wave;
+// }
+
+// struct com_snd_oscs_sawtooth {
+//   float v, a, i;
+// } com_snd_oscs_init_sawtooth(float frequency, float phase, float amplitude) {
+//   struct com_snd_oscs_sawtooth r;
+//   r.v = sinf(phase) * amplitude;
+//   r.a = amplitude;
+//   r.i = 2.f * frequency / STFU_AUDIO_FRAME_RATE * amplitude;
+//   return r;
+// }
+
+// /* Simple amplitude overflow check with truncation */
+// struct com_snd_oscs_sawtooth
+// com_snd_oscs_pump_sawtooth(struct com_snd_oscs_sawtooth wave) {
+//   wave.v += wave.i;
+//   if (wave.v > wave.a)
+//     wave.v -= wave.a * 2.f;
+//   return wave;
+// }
+
+#endif